Ground speed indicator



Aug. 22, 1950 AGlNs 2,519,422

' GROUND SPEED INDICATOR Filed March 6, 1946 STABLE PLATFO RM Fig.1

SHIP'S SPEED FRO L0 HIP'S SPEED FROM v F GYRO I 3! STABLE PLATFORM SHIPOR VEHICLE INVENTOR: George Agi'ns BY A wzz w Patented Aug. 22, 1950GROUND SPEED INDICATOR George Agins, Brooklyn, N. Y., assig'nor to AnnaCorporation, Brooklyn, N.Y., a corporation of New York Application March6, 1946, Serial No. 652,332

19 Claims.

This invention relates to speed indicators, and has particular referenceto mechanism for accurately measuring the speed of a ship or othervehicle in relation to the surface of the earth, with the use of agyroscope.

As is well known, a gyroscope which is mounted so as to be free of allrestraint will maintain its angular position in space, and thus appearsto tilt in its mounting about an axis which is the resultant of therotation of the earth and the travel of the mount, such as a ship, uponthe earths surface. If forces are applied to the gyroscope so as to justneutralize the effect of earth rotation, then the remaining tilt is thatdue to the travel of the ship on the earths surface. This tilt may beopposed by a precessional force so that the gyroscope remains tilted byan angle which is a measure of the ships angular speed rate, which may.be converted to linear ship speed by a simple calculation. Such anarrangement is a reliable measure of uniform or slowly changing shipspeed, but is too slow to change with change in vehicle velocity. Forcontinuous indication of rapidly changing ship speed, such as is metwith in evasive action in modern naval battles, for instance, such asimple device is impracticable. The diificulty has been, in pastpractice, that speed measurement by a ships log is not at all accurate,whereas speed measurement by a tilting gyroscope gives values widely outof phase with speed changes because of the great inertia of thegyroscope wheel.

In accordance with the present invention, a speed-indicating mechanismutilizing a gyroscope is provided, whose tilt is confined to thevertical plane of travel of the vehicle (a plane vertical to the horizonplane and containing, or parellel to, the fore and aft axis of thevehicle) and is proportional to the speed and wherein changes in speedare rapidly and accurately measured by pendulous means and directlyapplied to the gyroscope to correct its indication.

In a preferred embodiment of the invention, the universally-mountedgyroscope in neutral equilibrium is supported on a stable platform andis further stabilized against rotation of the earth, so that it tiltssolely in the plane of travel of the vehicle so that the tilt isa'continuous measare of the ships speed and may be transmitted to asuitable speed indicator or to calculating apparatus, such as gun firecontrol apparatus, or both. In order that the apparatus will not lagduring rapid speed and course changes of the ship, due to the inherentcharacteristics of the gyroscope, pendulous means responsive toaccelerations in the fore-and-aft plane, and to change in course in theathwartships plane, apply precessional torques around the propergyroscope support axes to thereby proportionally correct for suchchanges in speed and course. Means are also provided for placing theapparatus into immediate action with the aid of the ships log, instarting and in case the gyroscope has become de-energized.

It will be seen that the gyroscopic speed indicator of this invention isaccurate under all operating conditions, including rapid changes inspeed and course which are accurately measured and used to momentarilyprecess the gyroscope to keep its indication up to date, so that thegreat inertia of the gyroscope gives a reliable ripplefree indication ofship speed, and the acceleration measurements keep the indication of thegyroscope up to date, at all times.

For a more complete understanding of the invention, reference may be hadto the accompanying drawing, in which:

Figure 1 is a schematic mechanical and electrical diagram of thespeed-indicator of this invention as seen in plan; and,

Fig. 2 is a similar diagrammatic side View of the speed-indicator shownin Fig, 1.

Referring to this drawing, numeral It designates a gyroscope having itsspin axis arranged vertically and mounted on sensitive bearings II andI2 in a horizontal gimbal ring i3, which in turn is mounted in sensitivebearings l4 and IE on the phantom or follow-up frame 16 pivoted about aneccentric axis I! on a pedestal l8 fixed to the stable platform 39,carried on a ship or other vehicle whose speed is to be continuouslymeasured. Platform 59 may be stabilized in any suitable way, such as bya stable gyroscope vertical, an example of such stabilization beindisclosed in copending application Serial No. 607,614, filed July 28,1945, by applicant.

With the described mounting gyroscope ID has three degrees offreedom, 1. e., the instrument is universally mounted.

A servo-motor 26 is provided on the stable plati'orm l9 and arrangedthrough the gearing 21 to swing the phantom frame it in the plane ofvehicle travel about its axis ll in synchronism with the swinging of thegyroscope it about its corresponding axis 15-42. This follow-up actionof the gyroscope It by frame it is accomplished in well-known manner bynull coil 22 on the transverse axis trunnion of the gyroscope it, avoltage being generated in coil 22 upon relative angular movementbetween it and ar- I2 of the gyroscope I do not have any appreci-.

able relative rotation and accordingly the gyroscope IE3 is undisturbedby hearing friction.

However, the above-described arrangementis still responsive torelativemovement oi.the'ship in space, so that the gyroscope 'III willtiltfurther and further, in duplication of the angular travel of theship upon the earth 'and thd-mtw tion of the earth itself. Since thistilt is in-response to a displacement rather than speed, which is notdesired, itis corrected by an angle- "measur ing nullco'il 24 about axisI'I,"similar'"to coil-'22and'connected asshown irrfiigl1"to""amplifier='25. The relative tilt betweenpoil 24 and armature II'generates a' voltage-"proportional "to'the tilt in c'cil24;which;amp1ifiedirr 25j'is'fed intd'the circuit zdcontaining' thetorquen'rotor coil 21 "mounted" on frame 1 6 and'ha'ving in itsfl'eldthearmature I"'carried' by' gimbah'ifl, which accordinglyrespor'ids'to thisfieldandjapplies torque to the connected gyroscope I0around the axis I4; I5. "i'This torque-is ofsuch f'polaritythat'it'causes precession of the gyroscope around its axis II,I2','in.oppoSitedirectiom-to ,thenatur'al tilting above described sothat, when -thecorrection for earths rotation is appliedyand equilibriumis found, the: offset" angle of the gyroscope"- Iflrand itsj' phantommember '15 "from "vertical is ameasure of ships angularflspeedf asindicated on theoutput shaft 28 of the" motor '20. "This angle is' fedby'shaft28 into a suitable calculator 2 9, where;- by'mechanism;"wellknown, the angular .speed valueis changed to linearorsu'rfacespeedvalue; whiclrmaybefediasi at,v 30, to aniridicator 30,or"fire=contr'olor' othef'instruments, and at 3I "tothe"initiarsetupfievice 32; to be described.

In order that'theoutput 28"mayn'ot beimerror 'j because of the rotationof the earthjwhibhthe 'I gyroscope is unable to distinguish from ,Shjptravel, calculating mechanism of w'ellf-iknown ..'type is, provided at33"'in"Fig. l'to appIyfto-"the 1' gyroscopel U a counter-precessionequal'to the earthrotation effect on the same. *Thism'echa- "nism33"mayytake' the 'form ofpot'entiometertii having itsreslstance suppliedfrom the secondary winding of a transformer 34, whose primary *windingis energized from an alternating current source'35. A brush or slider 3Tonthe' resistance of' potentiometer 36 isadjustableby means"of"hand'-cranki38"in accordance with a functionthe angular velocityof thee'arth;and' Xisthe latitude. This voltage is fed to the'ist'ator'c'oil40' 'of an electro-magnetic resolver 4 I.

1 Resolver 4I comprises a rotor'hav ing' twodoils '42 and 43 mounted inspacequadrature inthe 'fieldof stator coil 40 and adjustabldangillarly",by shaft M in accordancewith' ships course. "Voltagesproportional totrigonometric functions -of'course Coand'angular rotationrate-of the--earth are accordingly induced in rotor"coils"'42 and43.*Further'details of this arrangement-are" 4 described in copendingapplication Serial No. 600,606, filed June 20, 1945, by applicant. Rotorcoil 42 thus delivers current of proper value to the motor 21 to exert atorque about axis I4, I5 5 causing precession of the gyroscope ID aroundthe athwart-ship axis II, I2, of sufficient magnitude toequalthe tiltdueto this component of earth rotation.

Similarly, the rotor c'oil 43 delivers current of u -proper value totorque motor 44 to exert a torque "about axis I II 2, causing precessionof the gyroi'scope' maround the fore-and-aft axis I4I5, of sufficientmagnitude to equal this component of .Zearth 'rotation. This circuit ofresolver coil 43 1.5 and torquemotor u also includes the output ofamplifier 45 actuated by the tilt measuring pick- *up coilui 'onathefore-and-aft axis I4I5, .whereby; any tendency of the free gyroscope I0to tilt over sidewise out of the vertical plane of vehicle travel iscorrected, this arrangement being "similar 'to' thatpreviously'described in connection with'amplifienfi.

I L'By means'of thesecorrecting mechanismsactingin 'concertfthegyroscope 'I 0 is protected from 25 all sources of error, so thatitsangleof tilt to the vertical'dsjat all-times ant-indication of'true orfgrouri'd speedof themounting ship or vehicle.

Thefgyroscope I I! is normally slow-acting and .thus"'som'etim'es maynotresp'ond' sufficiently gopromptly to-indicate-rapid changesin speed,and in order to expedite "its' response, the "pendulum resolver.unit'4I, is provided on the stable plat- "form 19. 'Resolver4Tcomprisesa shell havinga stator coil,".not"sh'own;butsimilar to'coil of re-35"solvei"4 I',.'energized front-the alternating currentsource'35'by'wires 48','*with' arotor coil similar to coi1"42or'- '43"of fres'olver'" 4 I" in inductive cooperatiorrwithi'the stator c'oiland'actuated angularly "by" the' 'simple pendulum '41 mounted to swin tofreelyin 'tnefore-and-ait plane-of ship trave1,as

shown. As the'rotor cdil -swings with thependuf'l'um'4I acurrentis'inducedtherein which is proportional to acceleration andhence'proportional ttochange'irrship-speed. This current is fedfrom 45unit. 41'by'tvires""49"Fig. 1, "into the circuit containing torque-coil21,"thus'causing a torque to beexertedabout axis "I4; 'I 5; resulting inacorresponding ipre'cession'of gyroscope 'I 9 about axis I IL-"I2,which; as previously explained; indicates "ehange its "responsespeed in conformity with-all rapid changesin "ship speed, andaccordingly 'be- -com'esan accurate groundispeed'indicator for all"conditions offoper'ation.

A"similarjpendiilum actuated unit is provided fat'illonthestableplattormI9, having its weight 5I arranged to'be responsive to a'thwartshipforces "due to accelerationswhich come'into action-upon "rapid changes'in'courseof the ship. The stator To "winding oithisunitfill is'energized'from alternating'current'source 'bylead's 52' and; asdescribed in connection withunit 41,1 a'current proportional warm-orpendulumflftvhich in't'urn is propor- "tionaltoacceleration,"is"generated in the rotor Ci-coil. This current is'red-bydeads' 53 through coil "43'? of resolver 4 I and the"outputcircuit of amblifler 45 into"'torque-coil:44 on gyroscope axis "II 1 2;"whi'ch'applies a torque' in the right sense *tdpreventdisplacement of the gyroscope out of l theverticahwhi'ch would'occur inrapid turns due i-to' fric'tion'in' the'sensitive'mounting bearings.

Becausefthe 'spin' wheel'of gyroscope I 0 is slow "to attaimsp'eedypnceit"has :become de'energized ""for anyi'reason' and displaced to someunpredictablepdsitionithegyroscope' is-notat once avail iable for ship.speed indication purposes, so that interim means 32 are provided, which,with the aid of the immediately available ships log speed indicator,places the invention into immediate use, both at the beginning and afterdeenergization for some reason. This unit 32 comprises a rotary driveshaft 54 carrying an arm 55 which has a contact wheel or trolley 56 forcontacting the concentric live segments 51 and 58 energized from centertap secondary winding of transformer 59, whose primar winding isenergized from the common source 35. Arm 55 is mechanically andelectrically connected to the arm 64 which has a contact wheel orcontrol 65 for contacting a concentric live segment 66 and dead segments6i and 68. Trolley shaft 54 is driven by the differential gearing 5|,one of Whose inputs, 62, is driven from the ships log, not shown, andwhose other input 3| is driven from the output shaft 33 of the speedindicator of this invention. In this way, the trolley shaft 54 alwaysindicates the difference between the ships log indication of speed andthe indication of the apparatus of re invention, the current flowingalong leads 60 being a constant current applied to the torque coil 2'5to initially rapidly erect the gyroscope It, whereupon the input 3| willsubstantially equal log input 52, thus causing differential St torestore trolley 58 to the insulation segment 63, and

trolley 55 to the live segment 66. This results in de-energization ofthe unit 32 since it is no longer needed, the gyroscope It then beingenabled to assume or resume its function of true ground speedindication, which appears on the shaft 39, as explained. Switch 69 isprovided to disconnect unit 32 after it has served its purpose. This .isaccomplished by switching movable contact from stationary contact H, tostationary contact 72.

Operation of the gyroscopic speed indicator of this invention, for shipsand other unstable vehicles, is readily understood from the foregoingand may be summarized as follows: The

I gyroscope iii, universally mounted in gimbals I3 and E6 on the ship orother vehicle, is stabilized against the instability of the vehicle, andis further stabilized against tilting clue to rotation of 1e earth bytorque motors 21 and 44 controlled by resolver ii in turn dependent uponlatitude adjustment 38, whereby tilting of the gyroscope 15 is duesolely to travel of the vehicle around the earth. The phantom member I6is powerdriven by motor 25 in response to tilt of the gyroscope Itdetected by unit 22, so as to follow the same in the vertical plane ofvehicle travel,

causing torque motor 21 to precess gyroscope It in opposition to thetilting due to vehicle travel,

whereby the resultant tilt angle of the gyroscope and the phantom member[6 is a continuous measure of the angular speed of the vehicle, which istransmitted by shaft 36 to a remote point, or is indicated on dial 3!),or both.

A stabilized acceleration unit 4! for measuring speed change of thevehicle develops proportional currents which are supplied by connections$9 to the torque-motor 21, whereby precessional torque is appliedcontinuously to the gyroscope to correct its speed indication 3i!momentarily by the measured acceleration. A second accelcrationunit 55on the stable platform measures angular acceleration due to change ofcourse of the vehicle and develops a proportional current, which is fedto a servo-system having a null coil pick-up 45 on the gimbal axis inthe plane of travel and applies torque to the gyroscope to pre- .46 andthe second acceleration unit 50.

vent deviation of the same but of the vertical plane of travel, thistorque being applied by a torque unit jointly responsive to the pick-upWhen the gyroscope Ill is started or restarted, means 32 responsive tovehicle speed value from a source 62 independent of the gyroscope l6initially erects the gyroscope.

Although a preferred embodiment of the invention has been illustratedand described herein, it is to be understood that the invention is notlimited thereby, but is susceptible of changes in form and detail withinthe scope of the appended claims.

I claim:

1. In a groundspeed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane, a gimbal support therefor, said support beingstabilized on said vehicle against the unstable movements of saidvehicle, the combination of means responsive to changes in position ofsaid vehicle for stabilizing said gyroscope against tilting due tomovement of the earth, electrical induction means responsive to relativeangular movement between said gyroscope spin axis and said support inthe plane vertical to the horizon plane containing the line of travel ofthe vehicle for developing voltage proportional to said angularmovement, a follow-up motor energized by said voltage and operativelyconnected to said support for adjusting the same in said plane torestore said electrical means to non-inductive position, and operativeconnections between said motor and said indicating member forpositioning the same in accordance with said angular movement asindicative of the speed of said vehicle in said plane.

2. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane, a gimbal support therefor having coordinatehorizontal axes, said support being stabilized against the unstablemovements of said vehicle, the combination of means responsive tochanges in position of said vehicle for stabilizing said gyroscope aboutsaid axes against tilting due to movement of the earth, electricalinduction means responsive to relative angular movement between saidgyroscope spin axis and said stabilized support in the plane vertical tothe horizon plane containing the line of travel of the vehicle fordeveloping voltage proportional to said angular movement, a follow-upmotor energized by said voltage and operatively connected to saidsupport for adjusting the same in said plane to restore said electricalmeans to non-inductive position, and operative connections between saidmotor and said indicating member for positioning the same in accordancewith said angular movement as indicative of the speed of said vehicle insaid plane.

.sponsiveto relative angular movement between 7 Lsaid gyro'scope spin;axis and s'aidistabllizedsupsport ."ingthe plane; vertical etc; the.horizomplane containing the. lineofrtravel-pf .the.=.vehicle-fordeveloping voltage proportional-(to; said angular ;-.movement,. afollow-upmotor energized by said L :voltage and operativelyconnected-toLsaid'support for adjusting .the: samednsaid-plane-to.-restore said parts of said electricalmeansitq non- -inductiveposition; and operative; connections-be- ,.-tween ,said motor.andsaidindicating .-member for; positioning. the. same in accordancelwitl'msaid :angular movement asindicative ofsthe speedof said vehicle.insaid. plane.

4. In a ground speed indicator for an unstable vehicle, including amovable indicating-am'ember, a. gyroscope havinga spin aaxis.iverticalvto, the ,hOIjZQl'l plane, a. gimbalysuppcrt.therefor-havingcoordinatehorizontal axesgsaid support-being stabilized; against the. unstableemovements. :of ;;said vehicle, the combination-of means responsive tochanges inposition of-.said.,vehicleifor v stabilizing said gyroscopeabout said axesagainst tilting due to movementof thejearth; electricalinduction means havingwrespective cooperating parts on said support and;onsaid; gyroscope ;re-

; -sponsive to relative angularmovementbetween said gyroscope spinaxisand .saidsupport in the plane'vertical to the horizon. plane.containing theline'of travel of the vehiclezfor'. developing voltageproportional to said; angularmovement,

a follow-up motor energized bysaid voltage and operatively connected-tosaid support for adjust- -ing the same in said plane :torestoresa'idparts I of said electrical meansytdnon-inductive position, and operativeconnections .between. said 7 motor and said indicating member forpositioning the'same in accordancewith' said;.angular movement asindicative f the spe ed:;,of.. said yohicle in; said plane.

5. -In a ground speed- -indicator forgan unstable 1 vehicle,- includingagnoyableyindicatinggmember, a gyroscope having; a ;.spin axis.vertical..-tc.z the hor z n pla a m al support. itherefor havingcoordinate horizontalaxes said support-being stabilized against :the;;unstable nmovements :of saidvehicle, the combination ;of ;electricalzmeans responsive to 'changes in position .of;.-said zvehicle due tomovement of the; earth ionideveloping voltages proportional to; therespective .-.anglesj-;of tilt, of said coordinate axes;;torque:motor=:means severally energized by..-said -;voltaees.-; to:..exert-v a torque on said gyroscope to-,-causeithe;same =to precessabout said coordinateyaxes: anamount equal to the tilt-about thecorresponding axes.=for stabilizing said gyroscope againstytiltingdue:.to movement of the earth,- electricalh -induction ,means responsive-torelatigve angular-movement be w en i yr op s nx xissand saidsu port inthe plane -vertical-to the-horizon. plane and containing'the -line.--oftravel ;of,-;;the vehicle for-developing a voltageproportionalsrtoz said 3 angular movement, afQllOWy-UP- motor .energizedby said voltage and operatively connected etc-said 'support ior{adjusting-the same! in :said plane to i restore 'saidelectrical means:to -non-inductive position; and operative .iconnecftionsbetweemsaidfollow-up motor and saidL-iindicating;.membergior positioning the same;in;.;accordance with; .;said angular movement asyindicatiye oftheespeed of said vehicle in said plane.

6. in a ground speedindicator for an. unstable vehicle, including amovable indicatingamember, a -gyroscope havingqa Spi :axis-.;vertical;.to-i-the diOri on "pl ne; a gimbal support athereior i hav-,;-;.-ing.-coordinate horizontalaxes, said suppontrbeing 4 8 istebilized.omsaid vehicle; against-.:.the -.unstable movements of said.vehicle',.:,the zcombination- .oi' electrical means responsiyextolzchanges. in =posie tionsofslsaid. vehicle .-ior ::.de;v.eloping .-.voltages pro- 5 --.por tional. to the respective; angles. ofatilt.offlsaid .-;.coordipate axes,g;tor.que motor-means severally energizedby said voltages toexert. autorquecon saidr gyroscope. to cause: thesame/to process about ysaidecoordinatel axes. an amount. equahtothe,tllt

10- about-the cor-responding. axeszfor stabilizing. said -gyroscopeagainst aitilting due;.. to movement xof 'gthe. .earth,:e1ectricaltinduction, means ,havingae- :zSDQtiVB cooperating .parts pmsaid support. and -on said gyroscopeiresponsivetto relative angular v;mQvement ;between-.,said gyroscope spin. axis. and --.8 iCt-' snpportointhe; plane :vertical to the horizon 8 plane andcontainingithe line, oftiavel of the ;ve- :---hi.cle ,for developing a voltage; proportional;to sa-id angular: movement; a, followvup. motor. energized ;-by said,voltage and. .operatively, connected to; said. support for,adjusting-:thezsameinssaid ulanesrto .restore asaid: parts :of;said;;;electrical means; r170 men-inductive .position; and ope 'ative-,.c'onnections. .between said ;fo1low:.up. .-motor and said-indicatingmemberlior, positioning the :same in accordance withasaid. angularmovement, as indicative. .of- :the speed of said, vehicle in said plane.

'7.-.;In a. groundspeed-indicator for an -unstable 3o vehicletincludingazmovable-indicating member, a; yros c ope having as-spin axis.vertical-mo :the 1 horizon plane, a gimbal asuspension :thereior;. asupport, said supportbeing stabilized against-the unstable; movements of.said -.vehicle; ,the combination of a frameicarryingsaidsupportand piv-.-;oted about; al orizontal axisnormal, to; the plane vertical,to.::the-;horizon planelcontainingathe line 0f; travel ot: the.=vehicle,l ,means-lresponsive to changes in position of said vehicleforgsta'biliz- .ggjngsaid gyroscope: against stilting due to moveomerit. of th earth; electrical induction; means .reispp si to-zreativeeangular movement-;;bet.ween said gyroscope spinaxis andsaiisnpportimthe plane Evertical. to the. horizonplane. and contain- 5,ing "15118;, line;oftravel 0.15 the .vehicle 5 for develop- 1 5 s zvoltaedntoportional to 1 said.. angular imov mont a follow-up motorenergizedbysaid .voltaeesand operativelyi-oonnected ,to saidiirametoradjusting .the; samejn said-gplane to restore said electricahmeans tooneinductive. position; and pperative ;-connections-.b.etween said motorand sa;id indicatin memberi or positioning the same in accordance.:with;;said angular movement; as dicative of thespeedmfi saidvvehicleein .said tsrpleu 8. Ina ground speed indicatouioran unstable vehi cle, including a movable.indicatingmember, j alygyroscqpe havingqa;s.pin..-axis, verticalz-to the horizon-plane, a-gimbal -suspensiontherefor,x.a support, -said:;supp.ort being stabilizedagainstthemllRSIrflblS movements, ot-said :vehicle; the :combination of. a'framecarrying said. support and. pivoted -abo uta horizontal axis.normalatozthe. plane verticalto the. horizonsplane and containing the 5line .of-travel of the .vehicle means responsive interchanges ii-position of saidvehicle for stabiliz- -ing-said gyroscope. against:tiltingdue to: movement: of, the earth; relectrical ;induction meanshaving-respective; cooperating parts on said-gyro- 70.. scope and'gimbal suspension responsive to role-- :r ivesansular movementbetween;said gyroscope spin :axis and rsaid sup ort in. thegplane :vertical11110 the horiz'onz'plane and v. containing theilineuof i. "travel ;ofthe vehicle-ifon'fieveloping voltage spro- 76 portional ..to a saidangular.movement a followup motor energized by said voltage andoperatively connected to said frame for adjusting the same in said planeto restore said parts of said electrical means to non-inductiveposition, and operative connections between said follow-up motor andsaid indicating member for positioning the same in accordance with saidangular movement as indicative of the speed of said vehicle in saidplane.

9. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane, a gimbal support therefor, said support beingstabilized on said vehicle against the unstable movements of saidvehicle, the combination of means responsive to changes in position ofsaid vehicle for stabilizing said gyroscope against tilting due tomovement of the earth, means responsive to acceleration of said vehiclefor modifying the response of said means, electrical induction meansresponsive to relative angular movement between said gyroscope spin axisand said support in the plane vertical to the horizon plane andcontaining the line of travel of the vehicle for developing voltageproportional to said angular movement, a follow-up motor ener'gized bysaid voltage and operatively connected to said support for adjusting thesame in said plane to restore said electrical means to non-inductiveposition, and operative connec-- tions between said motor and saidindicating member for positioning the same in accordance with saidangular movement as indicative of the speed of said vehicle in saidplane.

10. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane, a gimbal support therefor, said support beingstabilized on said vehicle against the unstable movements of saidvehicle, the combination of means responsive to changes in position ofsaid vehicle for stabilizing said gyroscope against tilting due tomovement of the earth, means responsive to acceleration of said vehiclein the plane vertical to the horizon plane and i containing the line oftravel thereof for modifying the response of said means, electricalinduction means responsive to relative angular movement between saidgyroscope spin axis and said support in the plane vertical to thehorizon plane and containing the line of travel of the vehicle fordeveloping voltage proportional to said angular movement, a follow-upmotor energized said voltage and operatively connected to said supportfor adjusting the same in said plane to restore said electrical means tononinductive position, and operative connections between said follow-upmotor and said indicating member for positioning the same in accordancewith said angular movement as indicative of the speed of said vehicle insaid plane.

11. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe 12. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane, a gimbal support therefor, said support beingstabilized on said vehicle against the unstable movements of saidvehicle, the combination of electrical means responsive to changes inposition of said vehicle for stabilizing said gyroscope against tiltingdue to movement of the earth, means responsive to acceleration of saidvehicle for developing a voltage proportional 1 modifying connectionsbetween said thereto, last-named and first-named means, electricalinduction means responsive to relative angular movement between saidgyroscope spin axis and said support in the plane vertical to thehorizon plane and containing the line of travel of the vehicle fordeveloping voltage proportional to said angular movement, a follow-upmotor energized by said voltage and operatively connected to saidsupport for adjusting the same in said plane to restore said electricalmeans to noninductive position, and operative connections between saidfollow-up motor and said indicating member for positioning the same inaccordance with said angular movement as indicative of the speed of saidvehicle in said plane.

13. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane, a gimbal support therefor having coordinatehorizontal. axes, said support being stabilized against the unstablemovements of' said vehicle, the combination of electrical meansresponsive to changes in position of said vehicle for developingvoltages proportional to the respective angles of tilt of saidcoordinate axes, torque motor means severally energized by said voltagesto exert a torque on said gyroscope to cause the same to precess aboutsaid coordinate axes an amount equal to the tilt about the correspondingaxes for stabilizing said gyroscope against tilting due to movements ofthe earth,

means responsive to acceleration of said vehicle for modifying theresponse of said torque motor 3 means, electrical induction meansresponsive to relative angular movement between said gyroscope spin axisand said support in the plane I vertical to the horizon plane andcontaining the line of travel of the vehicle for developing a voltageproportional to said angular movement, a follow-up motor energized bysaid voltage and operatively connected to said support for adjusting thesame in said plane to restore said electrical means to non-inductiveposition, and

operative connections between said follow-up motor and said indicatingmember for positioning the same in accordance with said angular movementas indicative of the speed of said vehicle in said plane.

14. In a ground speed indicator for an unstable vehicle, including amovable indicating member, a gyroscope having a spin axis vertical tothe horizon plane,: a gimbalsupport therefor having; coordinatehorizontaiv'axes; 1 said; support: bein-gz: stabilized againstthe.-unstabletmovementssofisaid vehicle-the combinationofzelectrical-zmeansr re-:esponsive to 'changesuin=positionrof saidvehicle: 5 forideveloping voltagesazproportionalaio theeree spectiveangles of tilt 'TOf'rSaid scoordinate v axes s. torques smotor meansseverally -.energized-:by 'said': voltagessio exert a 'torqueeonrsaidfgyrnscope. to: cause the same to precessaboutsaid coordinate; axes anamount equalztmthentiltz about theecorr-x responding axesa' forstabiiizingisaidngyroscopea against: tiltingsdue to-.:movementr.of'theszearth, means-responsivea-to acceleration :of said. vehicle" inrtheplanetvertioal toxthe horizon plane: and1'15.

containing the linewoftravelabf thezvehiclenand;in-zaqalaneanormalitheretolfordevelopingrzvolttageszproportionaletoxthecorresponding-v .tilt ofrvthe.gyroscope inf'saidij planes, connections:- rbetween saidslastsnamedmeans and theucorrespondingzrgg torquamotorxmeans .2 for modifying.izh-e response of said torque rmotorfmeanseaelectrical induction:meansiresponsive =to' -relative angulari movement? between rsaid'igyroscopeispin axis and saiddsupe port iinxsaids-iplane ofzrtraveloiithezl-vehiclefafori-"ea deaelopingrazvoltage'proportionalto'saidangular: movement: a follow up mortor energized'zbyirsaidivoltageand operatively :connectedrito"saidr:sup.+:-- port for adjustingthe. same-in'zsaid plane tosre-u store' said electrical-meanstCI'iIOIIeiHdLIOtiVG'IDOSi'e' 30.

tionrand; operative connections:..bet ween :said fol;-ldwauwmotorvandisaidsindicating member for positioning-nth; 'same in:accordancewwithP'sa'id' angular:movementxasiindicative ofithe:speed-son; saidvehicle .inisaid-planeis 3; :;Iria groundspeedzindicatorifor. an unstable vehiclegincl-udingi 12.: movable:indicating member; a gyroscoperhavings a zspin axist-verticat'; to; thehorizon plane, .azgimbahsupport therefor .havingaaz coordinate:rhorizontal iaxesyz said-:Isupport ibein'g (a stabilized againstthunstable movements ofvsaid vehicle; the combination-.131? =electrica1meansire---- sponsive to changesvinipositioniof saidvehicle-Torideveloping :yoltages':iproportionalftotxthe:respec l tiveangles-:ofetilt of.said.coordinateraxes;:torque-45nmtonmeansrseverallyenergized by. said-voltages: to: exert a:torqueixon: said .gyroscopeuto I cause-the same sto? precesst.aboutisaidicoordinate 1 axes':anamoilntsequai toethe:tilt about thecorresponding-r axes-.efon stabilizing saidsgyroscopei: against itilting: duei.=i1;o:1'mo.vemen-t ofnthe earth'," pendulum". meansnesponsiveto; acceleration :Of-J said :vehicle forrdevelopingaa voltage:-proportional- 130 the swing: ofithe pendulum,-connections between saidlasts-named meansand said torque motor m ans:

fornmdifying thewespcnse ofis'aid torque motor electricalaindnctiommeanswresponsiveto relative:zangnlaiermorementubetween:said gyroSOODCJESPiIIPG/XiSPQHQ saidssupport'zin'ethe :plane:

vertical toz-the: horizonzplame andcontaining the =(;0-

12 ing:coordinate:horizontalsaxes;::the;zcombinatiomofzelectricalimeanszresponsive to changes inposleltion' f said ivehicleforideveiopingiza voltage pro--=- portional rthereto; i attorque-imotoraresponsive ;to:: said voltage 'forcerecting said;gyroscope axis into: the plane vertical :to-i-thexhorizon :plane .andCOIL-i tainingisth'e :lineof travel iofsaid; vehicle; elec trical meansresponsive to relative movement be tween said gyroscope axis andsrsaidsuspension"; through ran :angle': insaiduplanei vfor A developing avoltagerproportional toasaid movement, a .fOllDWv up motor: venergized:ibya said last namedrvoltagee and operatively connected :to saidsuspension for; restoring -said suspensionwtlirough": said tangle, means-responsive tow-the speedrof said evehicle r relatively toatheseartmadiflerential jointly actur ated by said last-named means'randsaid:follow!v I upmotur; a :sourcewfcelectric power; a switch interposedbetween said-source andsaid torques;

motor fonerectin'g-said gyroscope, operativerconenectionszbetweensaid'fiifferential and saidi'switch forncontrollmg the sameyandoperative-conned tions c-between: saidi ifoilow-upx-motor ands-said?member forupositioning i-theusame as-indicative of the speed ofsaidxvehiclelin 'saidr plane.

1'2. 'In1a ground: speed (hidicator :for :an unstable vehicle,includingua fmovable"indicating-member, a gyroscope; having: a :spin:axis verticai to the horizon-plane; a gimbal-isuspension therefor:having coordinate-horizontal axes, th'e combinations ofr electrica'lmeans/responsive tochangesin-positioniof saidvehicleior developing avoltage proportionai Sto -the corresponding angle of tilt of I each ofsaid axesaa' torque motor responsive to eacnisaid voltage tor"-erectingsaid gyroscope spin axisinto': the plane svertical 1 to thehorizon .plane andconta'ining tlieline-of travel of said vehicle andior:stabilizingsaid-' otheraxis in the. coordi nate verti'cal planepelectrical 'means responsive to z relativewmovement between said"gyroscope: axis'and said suspension throughan angle in said planefoivdeveloping =a" voltage' proportional to i said :movement, a--foliowup' motor energized by said last-"named voltage'--and' operativelyconnectedstcrsaid:suspension-for restoring said suspension througli saidangleg means responsive'to the-'speed-ofi said vehicle -rela=tivelyto:the earth; a differential 'iointly actuated by said last-namedmeans-and said follow-up; motor; a source of electide-power; a" switchinterposed' between-said source and-one of said torquemotors forerecting sa d gyroscope; operative connections between saiddifferentialand said switch for controlling the same andoperative 1connections between said follow up motor *and said member forpositioningthe'--same :as indicat-ive of the speed of said 'vehicle in said planer18. Ina-ground speed indicator for an'unstable vehicle; amovable-indicating' member, a gyroscope havingits-spin axiscontained in-theplane vertical to the horizon-plane andcontaining the line of travelfofthe vehicle; gimbal suspension means for said gyroscope;-a support-forsaid gim bal suspension stabilized'ion the vehicle against theunstable-'movements thereofyandmeans for precluding angular displacementbetween the gyroscope" spin axis and said stabilized support due-"to-rotation'of theyearth; the combination, of electrical inductiommeans'responsive to angular-=displacementbetween 'said stabilized support-andsaid gyroscope'spinaxis-withinthe said verticai plane -as causedby-movement of said vehicle relativelyto"the-earth for developing avoltage proportional to --said *movement; means responsive" to theinduced voltage for "precessing said gyroscope to return the spin axisthereof in the direction of its initial angular position relatively tosaid support at a rate directly proportional to the angular displacementof said gyro spin axis relatively to said support, and means formeasuring the said angular displacement and for actuating saidindicating member in accordance with said angular displacement asindicative of the speed of said vehicle in said plane.

19. In a ground speed indicator for an unstable vehicle, a movableindicating member, a gyroscope having its spin axis contained in theplane vertical to the horizon plane and containing the line of travel ofthe vehicle, a gimbal suspension for the gyroscope, a first supportingmember for said suspension pivotally secured thereto, a second supportfor said first support pivotally secured thereto and stabilized againstunstable movements of the vehicle, and means for precluding angulardisplacement between said gyro spin axis and said stabilized support dueto rotation of the earth, the combination of first electrical inductionmeans responsive to angular movement between said gyro spin axis andsaid first support in said vertical plane for developing a first voltageproportional to said movement, means responsive to said voltage forpivoting said first support relatively to said second support to restoresaid first induction means to non-inductive relationship, secondelectrical in- 14 duction means responsive to pivotal movement betweensaid first and second supports in said vertical plane for developing asecond voltage proportional to said movement, torque means responsive tosaid second voltage for precessing the gyro spin axis toward itsoriginal angular relationship to said stabilized support at a rate whichis a function of the relative movement between said vehicle and theearth, and means responsive to the amount of angular displacementbetween said first and second supports for actuating said indicatingmember as indicative of the velocity of said vehicle in the saidvertical plane.

GEORGE AGINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,612,405 Weaver Dec. 28, 19261,692,412 Koenig Nov. 20, 1928 1,930,096 Henderson Oct. 10, 19331,933,493 Chessin Oct. 31, 1933 1,970,442 Wittkuhns et al. Aug. 14, 19342,346,798 Summers Apr. 18, 1944 2,411,087 Ford Nov. 12, 1946 2,412,614Haskins Dec. 17, 1946 2,427,158 Poitras Sept. 9, 1947

